Ooh! Team-up! Ordinarily I'd argue that five issues is far too soon in a new title's life to try something like this - you really should be concentrating on fleshing out your new characters, not displacing them with old ones - but Team America are sufficiently obscure for this to just about work.
Which is not to say I'm particularly impressed by them. Introduced only a year earlier in Captain America, only half of them are shown here - performing tricks at a carnival that the New Mutants are visiting. There's R U Reddy, a real candidate for the most badly-named character ever in a medium infamous for truly terrible monikers. Then there's El Lobo, a man so arrogant and self-regarding he not only talks in the third person but translates his own name after saying it. 
Also, some guy named Cowboy, who we don't care about. Calling someone on a bike Cowboy is stupid, anyway, no matter what Bon Jovi try to tell you. It's like calling an ironclad Unprocessed Ore.
We get a sweet moment from Roberto, whose desperate for autographs from Team America but insists their for his sister so as to remain cool (a goal already out of his reach, but it's fun to watch him try), and then all Hell breaks loose when green-clad goons crash the carnival and knock our patriotic biker squad from their
Said henchmen is, of course, the Silver Samurai. I hope that doesn't sound racist. I don't think all Asian men look the same when dressed as samurai. It's just that the other samurai don't make nuisances of themselves. They're happy enough to let their legend wind down. Not Kenuichio-san, though. He's on a mission to prove his honour by beating up some children. Nice.
After smacking Shan so hard she's knocked out and deflecting Cannonball into the nearby stands, the Samurai effortlessly defeats El Lobo, which is enough to finally bring out the Dark Rider. Imagine everyone's surprise when Harada chops DR's bike in half, pulls him from the wreckage, and unmasks him to reveal... Dani?
Rather put out by this strange development, the Silver Samurai teleports back to base, and takes Psyche with him, so his mistress Viper can sort it all out. With Karma unconscious and possibly concussed, and Sam barely able to stand, no-one is any position to stop him.
Later, Dani awakes. The black costume she wore as Dark Rider is gone, replaced with green clothes, presumably lifted from one of Viper's henchpeople. Viper herself has organised a little test for young Ms Moonstar: ride the nearby motorbike through an oncoming storm of giant spiked death wheels. Unfortunately, Psyche has never so much as touched a hog, and she comes within an inch of being squished almost immediately. Confused, Viper stops the trial, and has Kenuichio-san drag the teenager up to see her.
At this point, everyone's confused, including us. It's Dani that gets the worst of the deal, though; she's so scared and bewildered that she loses control of her powers, and gives Viper front-row seat to her own shell-scarred childhood. This, needless to say, does not go down well.
Whilst we speculate on what horrible revenge the former Madame Hydra has in store, and whilst Xavier - with help from Colonel Rossi, last seen in NMU #2 - tries to work out just what happened to Dani at the carnival, Viper takes a trip to see Honcho, head of Team America. Presumably, whatever she thinks is going on, she's prepared to assume kidnapping Psyche has removed the threat of interference from the Dark Rider. That makes more sense than the alternative reading: that now Viper has a hostage she can threaten if TA don't tow the line. It's not like young girls are in particularly short supply, for all that it felt that way when I was a teenager.
Viper's terms are simple: Team America lift something for her from a secret base in the Sierra Madre, or she kills Dani. For all Honcho knows, of course, Dani doesn't even exist (notably, Viper makes no effort to suggest executing the girl would cost TA the Dark Rider), but he agrees to play along, buying time for the rest of the team to arrive.
When the others do show up (summoned by the now-departed Viper), an argument breaks out between those who want to let Dani die (El Lobo), and those who aren't total arseholes (everyone else). Still, Honcho makes the smart point, which is they're not trading a heist for saving a hostage's life, they're trading a heist for the possibly saving a possible hostage. That's to say nothing of having any idea about who'll get it in the neck if Viper gets what she's angling for.
It's a nice, albeit brief, rise above the standard MO of comics of the period, in which a hero always does what a bad guy with hostages wants and always succeeds without causing any casualties and the villain always doublecrosses them and the hero always wins and saves the hostage anyway. Hearing someone say "Hang on, are we sure this is the right way to go" is new, and it's laudable. The conversation doesn't go any further, though, because Xavier arrives alongside the New Mutants, and lays down some truth for those assembled.
Charles, we learn, has figured out theat Team America is a "projecting gestalt", mutants that together impart their skills onto a random bystander in times of danger, up until now entirely without knowing it. This, of course, makes no sense. I mean, that's common enough for a Marvel superbeing, but how did they meet in the first place? They were all projectors and they liked motorbikes? Or is "loves crotch-rockets" a secondary mutation, now?
Leacing that aside, Xavier leads us into our second moral quandry in the issue: are Team America responsible for Dani's situation?
Now there's a question. Georginanna (TA's sole female member) argues that suggesting they are is deeply unfair. No-one chose to possess Dani; they never even realised such a thing was possible. There are things we're responsible for because we chose to do them, or we chose not to stop them. There are even things we're responsible for because we knew they were plausible results of our actions: I'm responsible for a seagull trapped in a sixpack holder I throw out without cutting up; it doesn't matter that I neither pulled it over the bird's neck myself, nor failed to chop up the plastic because I think seagulls have it coming to them. 
But who could see the ability to subconsciously possess people coming? "You heading to the pub, Frank? "Best not, Sally; I can't rule out the possibility that I could subconsciously possess someone along the way." Xavier's response is fascinating: once you know you're responsible for something bad, it's actually not as bad to have done it deliberately as it is to have done it accidentally, but not be bothered to fix it. Active evil is better than evil through selfish apathy, in other words, because it's not that your moral compass that's awry, it's your refusal to head in the direction it's pointing.
Obviously, there are limits to how far that argument can be taken - though it's particular apposite in this case when you realise that Team America held Dani hostage as surely as Viper did, and suppressed her sense of self at the same time - but Honcho buys it for now. This then triggers another crisis - Claremont is really cooking, here - because Xavier wants to play along with Viper, both to ensure Team America don't possess anyone else and to buy time for the X-Men to show up (they may well be overseas at this point, as we'll get to with the next UXM post).
The New Mutants see this plan as betraying Dani. What if Viper kills her whilst everyone's twiddling their thumbs? What if she's being tortured? Why does Xavier seem so keen on leaping to the aid of an entirely new group of mutants instead of focusing on the one he already has (this is something Xavier does an awful lot, as I argue here). This seems the least ambiguous of the dilemmas this issue presents; it's obviously better to send the X-Men in after Dani than the New Mutants, who already were soundly beaten by the Silver Samurai even when he was distracted by Team America. That said, it's hard to fault Roberto's reading of the professor's behaviour, because Charles is so awesomely terrible at actually explaining his motivations in any approachable way. Academics, huh?
It doesn't really matter who's in the right here, though. The New Mutants are heading out, and they're not coming back
This story takes place over a day and a night, leading in to early morning.
What? What? Tell us what's so clear to you, oh mighty Xavier!
"Team America is a projecting gestalt. In moments of extreme danger, any one of you can project the combined abilities of the team onto another, thereby creating the entity known as the Dark Rider. It is a form of possession. wherein the host consciousness is submerged beneath your group persona."
Oh. OK. Um... does Cerebro just inject LSD directly into your skull?
 This, of course, is just a particularly obvious and ridiculous example of an exceptionally irritating Claremont tic: to have foreign characters say brief phrases in their native language and then translate them into English. Which literally no foreign person I have ever met has ever done, unless I've said "I'm sorry, I don't understand; I know this is your country, but have you put more effort into international communication than I ever did?" in-between.
 Though for the record, seagulls are one of the most unambiguous manifestations of evil to exist on our planet.